Hydroquinones
In the golf industry, hydroquinones are commonly used in preparing polyurea- and polyurethane-based compositions. The use of hydroquinones in rubber-based golf ball compositions is also known. For example, U.S. Pat. No. 6,339,119 to Ladd et al. discloses a golf ball containing a cover layer and a core layer, where the core layer is molded from a scorch retarding composition comprising a scorch retarding peroxide, an elastomeric polymer, and a crosslinking agent. The scorch retarding peroxide typically contains a free radical scavenger selected from the group consisting of benzoquinones, hydroquinones, phenols, benzaldehydes, cyclohexadiene-1-ones, and mixtures thereof. The amount of the free radical scavenger in the scorch retarding peroxide is preferably from about 0.01 parts to about 2 parts per 100 parts of the peroxide by weight.
U.S. Pat. No. 6,919,393 to Mano et al. discloses a solid golf ball comprising at least one layer of a core, and at least one layer of a cover formed on the core, wherein at least one layer including the innermost layer of the core is formed by vulcanizing a rubber composition comprising a base rubber, a co-crosslinking agent, a vulcanization initiator and a filler, the core has a center hardness in JIS-C hardness of 40 to 60, a surface hardness in JIS-C hardness of 80 to 95 and a hardness difference (B−A) between a hardness in JIS-C hardness at a distance of 5 mm from the center point of the core (B) and the center hardness (A) of not less than 1 to less than 10. The rubber compositions for the core can contain a hydroquinone compound.
U.S. Pat. No. 6,956,128 to Higuchi et al. discloses a zinc acrylate particle composition comprising zinc acrylate satisfying the conditions, (i) that the proportion accounted for by the zinc acrylate particles measuring not less than 300 μm in particle size as determined by the dry type method be not more than 20% by mass of all the particles, (ii) that the median of particle sizes as determined by the dry type method be in the range of 10-300 μm, and (iii) that the ratio of the median (A) of particle sizes as determined by the dry type method to the median (B) of particle sizes as determined by the wet type method exceed 2, and an anionic surfactant. The acrylic acid used to produce the zinc acrylate particle composition may contain therein such a polymerization inhibitor as hydroquinone or hydroquinone monomethyl ether.
U.S. Pat. No. 6,767,940 to Voorheis et al. is directed to a golf ball having a core and cover, particularly to a golf ball core formed from a composition including an elastomeric polymer, a free radical initiator, and at least one stable free radical. The composition can further include one or more free radical scavengers and scorch retarders to increase the scorch time of the elastomeric polymer. Suitable free radical scavengers include benzoquinones; hydroquinones; phenols; benzaldehydes; cyclohexadiene-1-ones; and mixtures thereof.
U.S. Patent Application Publication No. 2002/0052253 to Fushihara et al. discloses a one-piece solid golf ball formed from a rubber composition comprising a mixture consisting of polybutadiene (a) synthesized using nickel-containing catalyst and polybutadiene (b) synthesized using cobalt-containing catalyst and hydroquinone or derivatives thereof as a vulcanization stabilizer, wherein a Mooney viscosity and a weight ratio of the polybutadienes (a) and (b), an amount of the vulcanization stabilizer, a center hardness and surface hardness of the golf ball, and a difference between the maximum hardness and minimum hardness in the golf ball are adjusted to a specified range. Examples of vulcanization stabilizers include 2,5-di-t-butylhydroquinone, 2,5-di-t-amylhydroquinone, 2,6-dimethylhydroquinone, bromohydroquinone, 2,3,5,6-tetrachlorohydroquinone and the like.
U.S. Pat. No. 6,488,597 to Iwami et al. discloses, for example in Table 1 on page 5, the use of 2,5-di-t-butylhydroquinone as an antioxidant in a golf ball core formulation.
U.S. Patent Application Publication No. 2007/0213440 to Goguen et al. discloses the use of hydroquinone-containing rubber compositions in a variety of golf ball layers.
Additional background references include U.S. Pat. No. 6,919,393 to Mano et al., U.S. Pat. No. 6,956,128 to Higuchi et al., U.S. Patent Application Publication No. 2002/0052253 to Fushihara et al., and U.S. Pat. No. 6,488,597 to Iwami et al.
Resilient Cores
The primary source of resilience, as measured by coefficient of restitution (“COR”), in commercially available golf balls is polybutadiene rubber, which is generally used to form all or part of the core. It is known that the resilience of a golf ball core, at a given compression, may be increased by forming a core layer from a rubber composition comprising an organosulfur compound. However, organosulfur compounds can be expensive and can cause processing difficulties.
While the use of hydroquinones in rubber golf ball compositions has been disclosed, there is a need in the industry to broaden the applicability of such compositions to particular golf ball constructions having desirable spin, feel, and distance properties. The present invention provides such golf ball constructions through the use of a dual- or multi-layer core formed from a rubber composition comprising a base rubber and a hydroquinone.